We present a theoretical framework for the calculation of charge transport through nanowire-based Schottky-barrier field-effect transistors (FETs) that is conceptually simple but still captures the relevant mechanisms of the transport process [1]. Our approach combines two approaches on different length scales: (1) the finite element method is used to model realistic device geometries and to calculate the electrostatic potential across the Schottky barrier by solving the Poisson equation, and (2) the Landauer-Büttiker approach combined with the method of non-equilibrium Green functions is employed to calculate the charge transport through the device. Our model correctly reproduces typical I-V characteristics of FETs, and the dependence of the saturated drain current on the gate field and the device geometry are in good agreement with experiments. Our approach is suitable for 1D Schottky-barrier FETs of arbitrary device geometry and it is intended to be a simulation platform for the development of nanowire-based sensors.